... the [Christmas Island] rats were identified as another endemic species, the Maclear's rat. It seems that in the late 19th century, these rats were as numerous as the red crabs are today. Like the crabs they were scavenging creatures that lived in burrows on the forest floor, but the exact role they played in the ecology of the island will forever remain a mystery– for by 1903 the species was extinct, wiped out by an epidemic of trypanosome parasites introduced by ship-borne black rats...

Europe's dense urban populations cooked up lethal bioweapons, carried around the world by European animals.